The present invention generally relates to the preparation of semiconductor grade silicon crystals, used in the manufacture of electronics. More particularly, the invention relates to a device for feeding arsenic dopant into an apparatus for producing low resistivity silicon crystals.
Silicon crystal growth using the Czochralski (CZ) method involves changing the characteristics and properties of the silicon ingot being grown by adding a dopant material to the molten silicon before silicon ingot growth. A common dopant material used in this process is arsenic. Arsenic, however, is a volatile substance and problems often arise through conventional methods of introducing the dopant to the silicon melt.
One such method is to dump the dopant from a port positioned above the melt. However, because of the high temperatures of the process, there is a violent loss of arsenic to the argon gas environment above the melt. This results in the generation of oxide-particles which can prolong and compromise the crystal growing process. Thus, this method is very inefficient.
Another method uses a quartz vessel containing the dopant above the melt for introducing the volatile gas to the melt. This method can reduce loss of vaporized dopant if the vessel has a port extending into the melt. Regardless, these methods result in complicated operation and loss of volatile dopant. The present invention overcomes these difficulties and disadvantages associated with prior art processes by introducing the dopant to the melt at an upper surface of the melt.